1. Field of the Invention
The present invention relates to an ink jet printing apparatus and a method of controlling the printing apparatus, and more particularly to a control on an ejection performance recovery operation for maintaining an ejection performance of a print head in the printing apparatus and on a paper conveying operation in the printing apparatus.
2. Description of the Related Art
In an ink jet printing apparatus in general, to maintain the ink ejection performance of a print head in good condition, an ejection performance recovery operation is performed which sucks out ink from nozzles of the print head to discharge viscous ink and bubble mixed ink from the print head. As a drive source for this recovery operation, a mechanism has been known to use a motor for driving a conveying roller that conveys a print medium such as a print paper. With the drive source shared by different operations in this way, the number of drive motors can be reduced, allowing the printing apparatus to be reduced in cost and size.
There is a mechanism in which a plurality of rollers for conveying a print paper are used commonly to one driving motor. For example, a conveying roller installed downstream of a paper feeding part in a conveying path is capable of being rotated either in a forward or backward direction according to the direction in which the motor is driven. This allows a paper front end position adjustment to be made to correct an oblique conveying of the paper. On the other hand, an intermediate roller installed upstream of the conveying roller is composed to be rotated only in the forward direction, no matter in which direction the motor is driven. In the above described mechanism that performs the paper conveying using the plurality of rollers and a recovery operation of the print head by a single common motor, there is a case where some of the plurality of rollers may be driven even during the recovery operation. For example, when the motor is reversed in rotation direction to execute the recovery operation, the intermediate roller is rotated in a direction opposite to the direction of the motor drive and also opposite to that of the conveying roller that is driven by the same motor. Normally, this does not pose any serious problem because the recovery operation is not executed while a print medium is conveyed. However, when the recovery operation is executed with a print paper still remaining on the intermediate roller, which may occur as a result of multiple paper conveying, the two rollers rotating in opposite directions to each other convey the print paper and cause a paper jam.
As an approach to this problem, it is described in Japanese Patent Laid-Open No. 2001-129979 that the recovery operation is interrupted immediately after detecting a paper jam during the print head recovery operation. Then the user manually removes the paper for which the paper jam error has been annunciated and that, when the presence of paper is no longer detected by a paper jam sensor, the printing apparatus enters into a standby state for printing.
With the above described method of Japanese Patent Laid-Open No. 2001-129979, however, the paper jam that is caused by the reverse rotation of the roller during the recovery operation cannot be prevented. As a result of this, the paper jam error, when it occurs, needs to be cleared by manually removing the paper and therefore the printing apparatus is deemed not user-friendly.